Clinical Manifestations

The specific presentation of acute Q fever differs geographically (e.g., pneumonia in Nova Scotia and granulomatous hepatitis in Marseille), potentially reflecting differences in routes of infection or infecting strains; chronic Q fever almost always implies endocarditis.

• Acute Q fever: After an incubation period of 3-30 days, pts may present with flulike syndromes, prolonged fever, pneumonia, hepatitis, pericarditis, myocarditis, meningoencephalitis, and infection during pregnancy.
  • - Signs and symptoms are often nonspecific (e.g., fever, fatigue, headache, chills, sweats, nausea, vomiting, diarrhea, cough, and occasionally rash).
  • - Multiple rounded opacities on CXR in pts in endemic areas are highly suggestive of Q fever pneumonia.
  • - The WBC count is usually normal, but thrombocytopenia occurs. During recovery, reactive thrombocytosis can develop.
  • - Prolonged fatigue, along with a constellation of nonspecific symptoms (e.g., headaches, myalgias, arthralgias), can follow Q fever (post-Q fever fatigue syndrome).
• Chronic Q fever: Pts with C. burnetii endocarditis typically have prior valvular heart disease, immunosuppression, or chronic renal failure.
  • - Fever is absent or low grade; pts may be ill for >1 year before diagnosis.
  • - Valvular vegetations are seen in 21-50% of cases with transesophageal echocardiography but in only 12% with transthoracic echocardiography. The vegetations differ from those in bacterial endocarditis of other etiologies and manifest as endothelium-covered nodules on the valve.
  • - The disease should be suspected in all pts with culture-negative endocarditis.
  • - Although C. burnetii can be isolated by a shell-vial technique, most laboratories are not permitted to attempt isolation because of the organism's highly contagious nature. PCR testing of tissue or biopsy specimens can be used, but serology is the most common diagnostic tool; IFA is the method of choice.